System and method for automatic detection of power up for a dual-rail circuit

Abstract

A dual-rail memory circuit having a sleep generation circuit configured to prevent undesired currents from being generated during power-up and while transitioning power states. When a dual-rail memory circuit is powering-up or exiting from a sleep mode, the ramping up of various supply voltage nodes may occur at different rates. Thus, in a dual-rail memory circuit, a first voltage rail may be at voltage before a second voltage rail. Such a transient state of operation may lead to current spikes that unnecessarily draw power and introduce undesired inefficiency. An internal sleep signal generation circuit in a dual-rail memory circuit may be used to precisely control an internal sleep signal such that the transition from off or sleep mode to operating mode is set to assure that the supply voltage nodes are close enough to the at-voltage operating level before releasing the sleep mode.

What is claimed is: 
     
       1. An integrated circuit, comprising:
 a first circuit stage having an input node coupled to a first supply voltage node and configured to receive a first supply voltage, the input node coupled to an inverter having an output node; 
 a second circuit stage having a first auto-sequencing circuit configured to generate a first holding signal and a second auto-sequencing circuit configured to generate a second holding signal; and 
 a third circuit stage having a pull-up circuit controlled by the first holding signal and configured to hold the output node at a second supply voltage corresponding to a second supply voltage node until the first supply voltage exceeds a threshold and a pull-down circuit controlled by the second holding signal and configured to hold the output node at a reference voltage corresponding to a reference node until the first supply voltage falls below a second threshold. 
 
     
     
       2. The integrated circuit of  claim 1 , wherein the inverter further comprises:
 a first PMOS transistor having a control node coupled to the input node, a first conduction node coupled to the output node, and a second conduction node; and 
 a first NMOS transistor having a control node coupled to the input node, a first conduction node coupled to the output node, and a second conduction node. 
 
     
     
       3. The integrated circuit of  claim 2 , wherein the first circuit stage further comprises:
 a first diode-connected PMOS transistor having a first conduction node coupled to the second conduction node of the first PMOS transistor and having a second conduction node; 
 a second diode-connected PMOS transistor having a first conduction node coupled to the second conduction node of the first diode-connected PMOS transistor and having a second conduction node coupled to the second supply voltage node; 
 a first diode-connected NMOS transistor having a first conduction node coupled to the second conduction node of the first NMOS transistor and having a second conduction node; 
 a second diode-connected NMOS transistor having a first conduction node coupled to the second conduction node of the first diode-connected NMOS transistor and having a second conduction node coupled to the reference node. 
 
     
     
       4. The integrated circuit of  claim 3 , wherein the first circuit stage further comprises:
 a first trimming PMOS transistor coupled in parallel to the second diode-connected PMOS transistor; and 
 a first trimming NMOS transistor coupled in parallel to the second diode-connected NMOS transistor. 
 
     
     
       5. The integrated circuit of  claim 1 , wherein the second circuit stage further comprises:
 a first PMOS transistor having a control node coupled to the output node, a first conduction node coupled to the second supply voltage node and a second conduction node; 
 a first NMOS transistor having a control node coupled to the output node, a first conduction node coupled to the first supply voltage node and a second conduction node coupled to the second conduction node of the first PMOS transistor; 
 a second PMOS transistor having a control node coupled to the output node, a first conduction node coupled to the first supply voltage node and a second conduction node; and 
 a second NMOS transistor having a control node coupled to the output node, a first conduction node coupled to the reference node and a second conduction node coupled to the second conduction node of the second PMOS transistor. 
 
     
     
       6. The integrated circuit of  claim 1 , wherein the third circuit stage further comprises:
 a first PMOS transistor having a control node coupled to receive the first holding signal, a first conduction node coupled to the second supply voltage node and a second conduction node; 
 a second PMOS transistor having a control node coupled to the first supply voltage node, a first conduction node coupled to the second conduction node of the first PMOS transistor and a second conduction node coupled to the output node; 
 a first NMOS transistor having a control node coupled to receive the second holding signal, a first conduction node coupled to the reference node and a second conduction node; and 
 a second NMOS transistor having a control node coupled to the first supply voltage node, a first conduction node coupled to the second conduction node of the first NMOS transistor and a second conduction node coupled to the output node. 
 
     
     
       7. The integrated circuit of  claim 1 , further comprising a dual rail memory. 
     
     
       8. The integrated circuit of  claim 1 , further comprising a single integrated circuit die.